Variable grid leak



Sept. 7 1926; 1,599,225

y A. FRANKLIN VARIABLE GRID LEAK Filed oct. 5. 1/922 MEM v lum i- -39INVENTOR A TTORNE Y Patented Sept. 7, 1926.

l UNITED STATES PATENT OFFICE;

ALBERT FRANKLIN, 0F NW YORK, N. Y., ASSIGNOR T0 CHAS. FRESHMN CO. INC.,

OF NEVI YORK, N. Y., A CORPORATION 0F NEW YORK.

VARIABLE Garn Laax.

Application filed October 5, 1922. Serial No. 592,574.

This invention relates to improve-ments in electrical apparatus withspecial re ference to devices known as variable resistances or grid leakin which the obstruction to flow of the current may be increased ordiminished. f One of the objects of the invention is to provide aresistancel of the type described in which the conductivity of theapparatus may be varied minutely, the adjustment being graduated fromsubstantially zero to full capacity.

Another purpose is in the provision yof an enclosed conductor the,resistance of, which can be varied from its exterior in a known degree,the same being indicated as operated and capable of being accuratelyreset to.obtain like results. f

A further aim is to produce a neat and Vcompact apparatus, comprised offew and simple parts arranged for convenient and easy operation andrelatively inexpensive 0 them` sald conductor making intimate electricalcontact with the exposed and coated to construct.

These and analogous aims, objects and purposes are accomplished by. thenovel structure hereinafter described rand illustrated in theaccompanying drawing, forming an essential part of this disclosure, andin whiclizA Figure 1 is a plan view of one embodiment of the invention.

Figure 2 is a central longitudinal sectional view of vthe same.

Figure 3 is a perspective view of a grid leak plate and means forvarying its resistance, the same being a simple form of the invention.

Y Figure 4 is a sectional view showing a further modification Vinconstruction.

As shown in the drawing the apparatus comprises an elongated rectangularhousing Y or body 10 made of insulating material, as rubber, fiber,porcelain or other dielectric substance,ithe same having an openrectangular recess 11 in its bottom.

A pair of binding osts, respectively 12 and 13, are fixed in sai body toextend above thesurface near its ends, the same being provided with theusual means for connecting with conducting-wires, the lower ends of theposts entering the recess 11.

Encircling the inreaching ends of the posts and in electrical engagementtherewith are metallic spacing collars 14 and 15 clamped by screws16 and17.

Seatedagainst the upper surface of the recess 11 and extending to coverits full area` is a grid leak plate 18 made of dielectric material butso treated, asby a coating of carbon or other conducting substance, asfito act as a weak conductor for electric currents passing from one postto the other, the stems of which engage the plate in addition to thecollars.

l 'l'hc stem 19 of a knurled knob 20 passes centrally through the body10 and plate 18, and carried by the stem 19, below the knob, 1s apointer 21 co-operating with a Acurved row of graduations 22 imprintedon the surface of the body l0 as shown in Figure'l.

Carried by the lower extremity of the knob stem 19 is a metallicconducting strip having., two equal tapering ends 23 and 24 rounded attheir extremities and so proportioned as to nearly touch the collars 14and 15 when the stripconductor is turned by the knob 20 to extend inregister between tors` its upper Surface being treated to ren Y der itweakly conductive, and the strip conductor 23 and 24 operated over itstreated or coated face by the knob 20', the broken lines showing theconductor as disposed transversely and hence substantially inoperativewith reference to conducting current from one terminal to the other.

It will be apparent that when the conductor-elements 23 and 24 or 23 and24 are directed to the terminals that they act as bridges conveying themaximum of current from one to the kother and thatby turning the knobthe conductivity ofthe grid leak plate will be reduced proportionatelyto ractically nothing, the position of the con- Y uctor elements bemgindicated by the grad nations 22.

Returning to the embodiment shown in Figures 1 and 2, it will be seenthat the screws 16 and 17 pass through the ends 27 and 28 of a'condenser29 disposed in the recess 11, said recess being rendered air-tight 4,the casing is omitted and the arrangement of parts slightly varied.

A similar knob 32 is engaged on the screw-threaded stem of a stud 33which carries a double ended conductor strip having opposed elements 3ftand 35 in electrical. engagement with the coated dielectric grid leakplate 36, the same being in contact with a condenser member.

Said member is secured at one end by a grommet terminal 38 and isseparated from a similar member 39 by the interposition of a sheet'ofmica 40 or like material.

The condenser member 39 is secured by a grommet terminal 4l, and held byan insulated backing plate 4Q, all of the several plates being firmlyunited by the grommets as shown, and obviously the operation is like theother devices described and by which similar results are. attained.

Although the invention has been described With considerable detail andWith respect to certain particular forms, it is not desired to belimited to such details since many changes and other modifications maywell be made Without departing from the spirit and scope of theinvention in its broadest aspect.

Having thus described my invention, what I claim is new and desire tosecure by Letters Patent, is

l. An electrical apparatus comprising a dielectric plate, a conductingcoating on one -side thereof, terminals for connecting an plate haring asurface of weak conductivity, A

terminals for connecting an electric current to the opposite ends ofsaid plate surface, an elongated strip conductor pivoted centrally onsaid plate with its entire contiguous surface in constant electricalcontact with the conductive surface thereof, means for rotating saidconductor into varying angular positions relative to said terminals, andmeans for registering the position of said conductor.

Signed at New York in the county of New York and State of New York this30th day of September A. D. 1922.

ALBERT FRANKLIN.

